Fuel-air mixture control for internal combustion engines



Sept. 10, 1940.

FUEL-AIR MI 7'0 Zwcnnws fun.

A. SCHWEIZER ET AL 2,213,997

XTURE CONTROL-FOR. INTERNAIQ COMBUSTION ENGINES Filed March 22, 1938 Fly. 1

Patented Sept. 10, 1940 UNITED STATES PATENT OFFICE FUEL-AIR IlIIXTURE CONTROL FOR INTERNAL COMBUSTION ENGINES Application March 22, 1938, Serial No. 197,456 In Germany April 1,1937

9 Claims. (Cl. 123- 136) The present invention relates to devices for adjusting the ratio between air and fuel supplied to internal combustion engines of the type wherein a thermostat is provided influencing the mixture formation according to requirements.

The function of the thermostat usually is to adapt the fuel supply to the air charge, which varies with the temperature. In certain circumstances, it is very desirable. with devices of ii) this type however, to be able to adjust the control member acting on the fuel supply, independently of the temperature prevailing in the supply pipe of the engine. For instance, during the take-off of an aircraft or during flight when unl5 der full or substantially maximum load, the internal combustion engine should preferably be driven with a richer mixture than the mixture control, set with regard to normal conditions, would deliver consequent on existing operating conditions (air pressure and air temperature). Similar demands are also made of motor vehicles, especially those provided with charging blowers. Q The problem characterised above is solved by the fact that according to the invention, the thermostat is arranged so as to be movable.

The invention is more particularly described with reference to the accompanying drawing; which illustrates one form of construction by' way of example and in which:

Figure 2 illustrates a' practical form of construction of thermostat shown diagrammatically in Figure 1.

In a casing III, which is adapted to be secured by a flange H!" with the casing of an injection pump Aiof an internal combustion engine 3 a housing having end walls l2 and I3 is mounted so as to be longitudinally displaceable therein,

In the interior of the housing I there is provided a bellows like metal diaphragm l5, which is securely attached at one end to the wall l2, and which, with an end.plate l6 fitted'to its free end, is adapted to adjust the position of a displaceable spindle which is guided in the end wall I3, and is loaded by a spring l8. To this spindle is fitted a bracket having a pivot IQ for a two-armed lever 20 which extends througi. a slot H in the housing One arm of the lever 20 is connected in known manner by means of a link rod 2| with the usual control member 22 of injection pump A while the other arm of the lever has a pin and slot connection with aspindle 26 carrying a diaphragm 25. Movement of the rod 2| and control member J5 22 to the right in the direction of the arrow in Figure 1 is a diagrammatic representatiomand Fig. 1 increases the fuelsupply delivered by pump A. The diaphragm 25 and the spindle 26 are accommodated, together with a spring 21 serving to guide the shaft, in a casing part 30, which part is attached to the casing l0 and is provided with a cover 3|. In the hollow space of this cover which is connected by a pressure supply pipe 29 with an air feed pipe 32 of the internal combustion engine B, there is disposed a return spring 28, which abuts against an adjustable support in the cover 3|.

A lever 33 is flexibly connected to the end wall |2 of the housing H, and is pivoted to a spindle 34, which penetrates the casing l0 and is connected outside the casing with a lever 36. The lever 36 isconnected by a link rod 31 with one arm 38 of a' lever, the other arm 39 of which, under the action of a spring 23 operating on the end stat and is flexiblyconnected to a manually operated setting member 45."

The method of operation of the device is as follows: When the speed of an internal combustion 21. This movement of the diap ragm 25 causes rocking movement of the lever 2 about the pivot l9, and a displacement of the control rod 22 into that position consistent with a decrease in the supply of fuel to the engine. The same thing occurs when the airstream is throttled by a throttle valve located in advance of. the point of connection of the pressure supply pipe 28 with the air feed pipe 32. The function of the diaphragm 25 is thus to adapt the supply of fuel to the number of revolutions of the engine, which varies with the position of the throttle valve, and to avoid exceeding the maximum number of revolutions diaphragm 25 and the force of te weaker spring .wall |-3 of the housing II, is positively connected i admissible under and with each of a number of different circumstances.

When the atmospheric air pressure drops, and thus the weight of air sucked in by the engine per stroke decreases, the bellows diaphragm 5 ex pands within the housing H and displaces the pivotal axis l9 of the lever 20 in such a way that the supply of fuel is likewise diminished by displacement of the control rod 22.

The same control movement takes place when the weight of air fed per stroke of the internal combustion engine diminishes by reason of the fact that the air temperature rises. Under such circumstances the housing II is displaced by the expansion member 35 of the thermostat 40 against the force of the spring 23 operating on the end wall |3, and by this means the pivotal point l9 of the lever 20 is likewise so displaced that it moves the control rod into a position in which the supply of fuel is throttled. If the aforesaid action of the members I5, 25, 35 or of one of them is to be temporarily suspended and more fuel is to be supplied in view of particular demands to be made of the engine, which difiers from those of normal operation, then the thermostat 40 is moved by the setting lever 45 against the force of the spring 43. This movement is followed, under the action of the spring 23, by the housing H and the parts connected therewith, the control rod 22 being so moved that the supply of fuel is increased. The spring 43 must be stiffer than the spring 23, so that, after the setting lever 45 has been returned into its original position consistent with normal operations, the control rod 22 can again take up its normal position determined by the position, at the time of return,

of the expansion member 35 and of the remain-.

ing adjusting members I5 and 25. By reason of this relatively greater stiffness the control rod can follow any alterations in the positions of the adjusting members While the lever 45 remains in its normal or inoperative position.

In the operation of vehicles for aircraft, especially in the case of internal combustion engines with a charging blower it is often desirable, after a predetermined temperature has been reached by the air flowing to the cylinders, to prevent further decrease in the supply of fuel. This requirement can be met by the provision of an adjustable stop 5| in the path of movement of the lever arm 38. This stop terminates the adjusting movements of the thermostat after a predetermined limit of temperature, which can be set to suit varying conditions, has been reached so that in the event of an expansion of the temperature sensitive member 35 of the thermostat occurring as a result of further rise in temperature, the thermostat 40 is pushed further into the air feed pipe against the action of the spring 43, without in any way affecting the mixture control.

In the example of construction shown in Fig. 2, the thermostat 40, together with the spring 43 located between the collar 42 and a guide ring 52, are inserted into the sleeve 4| the unit being held therein by means of. a snap ring 53. The sleeve has a thread 54 by which it is screwed into a bore in the air feed pipe 32 of Fig. 1. In that part of the sleeve 4| which projects outwardly from the pipe 32 and which has a thread 56, there is guided so as to be longitudinally displaceable a temperature sensitive part of the thermostat 40 terminating in the end surface 46. On to the thread 56 there is screwed a tubular hollow element 55 having a longitudinal slot 51. Through this slot project the lever arms 48 and 38 already described with reference to Fig. 1, and an extension 58 of a hollow cap 50, on which the pivots 49 and 59 of the lever arms are mounted. By virtue of the extension 58, the cap 50 is guided on the hollow element 55 so that it is longitudinally displaceable, but is incapable of rotation; the cap, however, can be rocked slightly relatively to the bush 4|, into any desired position, i. e., a position suitable for the connection of the rods, for in-,

stance, of the link rod 37, without jamming of the levers 39 and 48 on the side surfaces of the slot 51. The cap is firmly pressed on to an end surface SI of the bush 4| by means of a cap nut 60, which is screwed on to a thread '32 on the outer end of the hollow member 55. The adjustable stop 5| described in Fig. 1, is fixed in the cap nut 60. The lever arm 48 is bifurcated at that end which bears on the end surface 46, so that it embraces the adjusting member 35, which projects from this end, and the part adjacent thereto of the lever arm 39.

With the parts serving for the occasional displacement of the thermostat 40, e. g., the bell crank lever 48, 41, further regulating devices serving for the control of the internal combustion engine may be connected, e. g., a throttle valve operating on the air feed may be provided in the pipe 32, or a control member influencing the air delivery of a charging blower.

We declare that what we claim is:

1. A fuel controlling device for internal combustion engines, comprising at least one element for controlling the fuel supply to said engine, a thermostat in the air feed to said engine the temperature sensitive element of which thermostat is adapted to displace said control element on variation in temperature of said air feed, manually op erable means for adjusting the position of said thermostat bodily to vary the basic temperature at which said temperature sensitive element dis places said control means, and means associated with said manually operable means for varying the volume of air fed to said engine.

2. A fuel controlling device for internal combustion engines comprising a holder, at least one element carried by said holder for controlling the fuel supply to said engine, a thermostat associated with said holder for bodily displacement therewith, and having a temperature sensitive element adapted to displace said control element, resilient loading means between said thermostat and said holder, and means for displacing said thermostat relatively to said holder against said resilient load to vary the relationship between said temperature sensitive element and said control element to vary the extent of displacement of said control element by said temperature sensitive element while still leaving said latter element under the control of said temperature sensitive element.

trol element to displace said control element on variation in temperature of said air feed, a bushing within which said thermostat is resiliently mounted for relative longitudinal displacement therein, a hollow cap associated with said bushing and within which said temperature sensitive element extends, a pivot for said control element on said hollow cap, and a lever on said hollow amass? cap for displacing said thermostat bodily within said bushing to vary the extent of displacement of said control element by said temperature sensitive elementwithout destroying said operative connection between said temperature sensitive element and said control element.

4. A fuel controlling device as claimed in claim 3 and wherein said control element comprises a lever pivotally mounted to said hollow cap and wherein said lever is bifurcated at one end to embrace the other control lever and the temperature sensitive element whereby said control lever is positively engaged with said temperature sensitive element and said bifurcated lever is engageable with the end of the body of said thermostat.

5. A fuel controlling device as claimed'in claim 3 and wherein said hollow cap is rockable slightly relatively to said bushing for assisting in'the assembly oi the elements associated therewith.

6. A fuel controlling device as claimed in claim 3 and including a hollow tubular elementwithin said hollow cap rotatably fitted on said bushing, said hollow tubular element receiving said hollow cap so as to permit oi relative longitudinal displacement therewith, and means whereby after,

said cap has been slightly rocked into position suitable for installation, said cap is secured in adjusted position on the bushing of saidthermostat. a f

7. A fuel controlling device as claimed in claim 3 and wherein stop means are provided for limiting the adjustment movements of the temperature sensitive element of said thermostat alter a predetermined temperature has been reached whereby inthe event oi further displacement 0! said temperature sensitive element relatively to the body of said thermostat the latter is bodily displaceable against its resilient load.

8. A iuel controlling device as claimed in claim 3 and wherein adjustable stop means are provided ior limiting the adjustment movements of the temperature sensitive element of said thermostat after a predetermined temperature has been reached and the resilient mounting'oi the thermostat includes a spring carried by said bushing whereby in the event of further displacement of said temperature sensitive element relatively to,

the body ofsaid thermostat the latter is bodily l displaceable against its resilient load.

9. A iuel controlling device for internal combustion engines; having an air feed pipe, operable in varying altitudes and by which the fuel supply is-controlled both by means influenced by the speed of the engine or by a'value dependent thereon such as the pressure in the air teed pipe or a pressure diflerence produced in said pipe,

and by an adjusting member influenced by at-- mospheric air pressure, comprising a control rod for 'the fuel supply of said engine. adjusting means corresponding to variations in air pressure operatively connected to said control rod, a

thermostat, the temperature sensitive element of which is positively connected with said control rod to displace the latter on variation in air temperature and means for bodily adjusting the position of said thermostat relative to said control member to vary the extent of displacement of said control rod by said temperature sensitive element. 1 

